Basic Structure of a Cell
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1
Review Facts
About Living
Things
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What Are the Main
Characteristics of organisms?
1. Made of CELLS
2. Require ENERGY (food)
3. REPRODUCE (species)
4. Maintain HOMEOSTASIS
5. ORGANIZED
6. RESPOND to environment
7. GROW and DEVELOP
8. EXCHANGE materials with surroundings
(water, wastes, gases)
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LEVELS OF ORGANIZATION
Nonliving Levels:
1.ATOM (element)
2.MOLECULE (compounds like
carbohydrates & proteins)
3.ORGANELLES (nucleus, ER, Golgi …)
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LEVELS OF ORGANIZATION
Living Levels:
1.CELL (makes up ALL organisms)
2.TISSUE (cells working together
3.ORGAN (heart, brain, stomach …)
4.ORGAN SYSTEMS (respiratory,
circulatory …)
5.ORGANISM copyright cmassengale
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LEVELS OF ORGANIZATION
Living Levels continued:
1.POPULATION (one species in an area)
2.COMMUNITY (several populations in
an area
3.ECOSYSTEM (forest, prairie …)
4.BIOME (Tundra, Tropical Rain
forest…)
5.BIOSPHERE (all living and nonliving
things on Earth)
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6
History of Cells & the
Cell Theory
Cell
Specialization
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First to View Cells
• In 1665, Robert
Hooke used a
microscope to
examine a thin
slice of cork
(dead plant cell
walls)
• What he saw
looked like small
boxes
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First to View Cells
• Hooke is
responsible for
naming cells
• Hooke called them
“CELLS” because
they looked like
the small rooms
that monks lived in
called Cells
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9
Anton van Leeuwenhoek
• In 1673,
Leeuwenhoek (a
Dutch microscope
maker), was first to
view organism (living
things)
• Leeuwenhoek used a
simple, handheld
microscope to view
pond water &
scrapings from his
teeth
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Beginning of the Cell Theory
• In 1838, a
German botanist
named Matthias
Schleiden
concluded that all
plants were made
of cells
• Schleiden is a
cofounder of the
cell theory
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11
Beginning of the Cell Theory
• In 1839, a
German zoologist
named Theodore
Schwann
concluded that
all animals were
made of cells
• Schwann also
cofounded the
cell theory
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12
Beginning of the Cell Theory
• In 1855, a German
medical doctor named
Rudolph Virchow
observed, under the
microscope, cells
dividing
• He reasoned that all
cells come from other
pre-existing cells by
cell division
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CELL THEORY
• All living things are
made of cells
• Cells are the basic unit
of structure and
function in an organism
(basic unit of life)
• Cells come from the
reproduction of existing
cells (cell division)
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14
Discoveries
Since the Cell
Theory
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ENDOSYMBIOTIC THEORY
• In 1970, American
biologist, Lynn Margulis,
provided evidence that some
organelles within cells were
at one time free living cells
themselves
• Supporting evidence included
organelles with their own
DNA
• Chloroplast and
Mitochondria
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Cell Size and Types
• Cells, the basic units of organisms, can
only be observed under microscope
• Three Basic types of cells include:
Animal Cell
Plant Cell
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Bacterial Cell
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Number of Cells
Although ALL living things are made of
cells, organisms may be:
• Unicellular – composed of one cell
• Multicellular- composed of many cells
that may organize into tissues, etc.
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19
CELL SIZE
Typical cells range from 5 – 50 micrometers (microns)
in diameter
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cmassengale
20
Which Cell Type is Larger?
Plant cell > _____________
Animal cell > ___________
bacteria
_________
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21
How Big is a Micron ( µ ) ?
1 cm = 10,000 microns
1” = 25,000 microns
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22
Multicellular Organisms
• Cells in multicellular organisms often
specialize (take on different shapes &
functions)
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Cell Specialization
• Cells in a multicellular organism
become specialized
by turning different
genes on and off
• This is known as
DIFFERENTIATION
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Specialized Animal Cells
Muscle cells
Red blood cells
Cheek cells
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Specialized Plant cells
Guard Cells
Pollen
Xylem cells
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Organization Levels
of Life
Atoms to Organisms
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Nonliving Levels
ATOMS 
MOLECULES
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 ORGANELLES
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Living Levels

CELLS – life
starts here
TISSUES – Similar cells

working
together
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More Living Levels
ORGANS
Different tissues
working together

ORGAN
SYSTEMS
Different organs
working together
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
ORGANISM
30
Simple or Complex
Cells
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Prokaryotes – The first Cells
• Cells that lack a nucleus or
membrane-bound organelles
• Includes bacteria
• Simplest type of cell
• Single, circular chromosome
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Prokaryotes
• Nucleoid region
(center) contains
the DNA
• Surrounded by cell
membrane & cell
wall (peptidoglycan)
• Contain ribosomes
(no membrane) in
their cytoplasm to
make proteins
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Eukaryotes
• Cells that HAVE a
nucleus and membranebound organelles
• Includes protists,
fungi, plants, and
animals
• More complex type of
cells
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Eukaryotic Cell
Contain 3 basic cell
structures:
• Nucleus
• Cell Membrane
• Cytoplasm with
organelles
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Two Main Types of
Eukaryotic Cells
Plant Cell
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Animal Cell
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Organelles
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Organelles
• Very small (Microscopic)
• Perform various functions for a
cell
• Found in the cytoplasm
• May or may not be membranebound
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Animal Cell Organelles
Ribosome (attached)
Ribosome (free)
Nucleolus
Nucleus
Cell Membrane
Nuclear envelope
Mitochondrion
Smooth
endoplasmic
reticulum
Rough
endoplasmic
reticulum
Centrioles
Golgi apparatus
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Plant Cell Organelles
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Cell or Plasma Membrane
• Composed of double layer of phospholipids and
proteins
• Surrounds outside of ALL cells
• Controls what enters or leaves the cell
• Living layer
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
of cell
(cytoplasm)
Protein
channelcopyright cmassengale
Lipid bilayer
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Phospholipids
• Heads contain glycerol &
phosphate and are hydrophilic
(attract water)
• Tails are made of fatty acids
and are hydrophobic (repel
water)
• Make up a bilayer where tails
point inward toward each other
• Can move laterally to allow
small molecules (O2, CO2, &
H2O to enter)
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42
The Cell Membrane is Fluid
Molecules in cell membranes are constantly moving
and changing
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Cell Membrane Proteins
• Proteins help move large
molecules or aid in cell
recognition
• Peripheral proteins are
attached on the surface
(inner or outer)
• Integral proteins are
embedded completely
through the membrane
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44
GLYCOPROTEINS
Recognize
“self”
Glycoproteins have carbohydrate tails to act
as markers for cell recognition
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45
Cell Membrane in Plants
Cell membrane
• Lies immediately
against the cell
wall in plant cells
• Pushes out
against the cell
wall to maintain
cell shape
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46
Cell Wall
• Nonliving layer
• Found in plants,
fungi, & bacteria
• Made of cellulose in
plants
• Made of
peptidoglycan in
bacteria
• Made of chitin in
Fungi
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Cell wall
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Cell Wall
• Supports and
protects cell
• Found outside of the
cell membrane
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Cytoplasm of a Cell
cytoplasm
• Jelly-like
substance enclosed
by cell membrane
• Provides a medium
for chemical
reactions to take
place
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49
More on Cytoplasm
cytoplasm
• Contains organelles
to carry out
specific jobs
• Found in ALL cells
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The Control Organelle - Nucleus
• Controls the normal
activities of the cell
• Contains the DNA in
chromosomes
• Bounded by a
nuclear envelope
(membrane) with
pores
• Usually the largest
organelle
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51
More on the Nucleus
Nucleus
• Each cell has fixed
number of
chromosomes that
carry genes
• Genes control cell
characteristics
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52
Nuclear Envelope
• Double membrane surrounding
nucleus
• Also called nuclear membrane
• Contains nuclear pores for
materials to enter & leave
nucleus
• Connected to the rough ER
Nuclear
pores
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53
Inside the Nucleus The genetic material (DNA) is found
DNA is spread out
And appears as
CHROMATIN
in non-dividing cells
DNA is condensed &
wrapped around proteins
forming
as CHROMOSOMES
in dividing cells
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54
What Does DNA do?
DNA is the hereditary
material of the cell
Genes that make up the DNA
molecule code for different
proteins
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Nucleolus
• Inside nucleus
• Cell may have 1
to 3 nucleoli
• Disappears when
cell divides
• Makes ribosomes
that make
proteins
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Cytoskeleton
• Helps cell maintain cell
shape
• Also help move
organelles around
• Made of proteins
• Microfilaments are
threadlike & made of
ACTIN
• Microtubules are
tubelike & made of
TUBULIN
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Cytoskeleton
MICROTUBULES
MICROFILAMENTS
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Centrioles
• Found only in animal
cells
• Paired structures near
nucleus
• Made of bundle of
microtubules
• Appear during cell
division forming mitotic
spindle
• Help to pull chromosome
pairs apart to opposite
ends of the cell
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Centrioles & the Mitotic Spindle
Made of MICROTUBULES (Tubulin)
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Mitochondrion
(plural = mitochondria)
• “Powerhouse” of the cell
• Generate cellular energy
(ATP)
• More active cells like
muscle cells have MORE
mitochondria
• Both plants & animal cells
have mitochondria
• Site of CELLULAR
RESPIRATION (burning
glucose)
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MITOCHONDRIA
Surrounded by a DOUBLE
membrane
Has its own DNA
Folded inner membrane
called CRISTAE
(increases surface area
for more chemical
Reactions)
Interior called MATRIX
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62
Interesting Fact --• Mitochondria
Come from
cytoplasm in the
EGG cell during
fertilization
Therefore …
• You inherit your
mitochondria
from your
mother!
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63
Cell Powerhouse
Mitochondrion
( mitochondria )
Rod shape
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What do mitochondria do?
“Power plant”
of the cell
Burns glucose to
release energy (ATP)
Stores energy as ATP
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Endoplasmic Reticulum - ER
• Network of hollow membrane tubules
• Connects to nuclear envelope & cell
membrane
• Functions in Synthesis of cell products &
Transport
Two kinds of ER
---ROUGH & SMOOTH
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Rough Endoplasmic Reticulum (Rough
ER)
• Has ribosomes
on its surface
• Makes
membrane
proteins and
proteins for
EXPORT out of
cell
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Rough Endoplasmic Reticulum
(Rough ER)
• Proteins are made
by ribosomes on ER
surface
• They are then
threaded into the
interior of the
Rough ER to be
modified and
transported
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Smooth Endoplasmic Reticulum
• Smooth ER lacks
ribosomes on its
surface
• Is attached to the
ends of rough ER
• Makes cell products
that are USED
INSIDE the cell
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Functions of the Smooth ER
• Makes membrane
lipids (steroids)
• Regulates calcium
(muscle cells)
• Destroys toxic
substances
(Liver)
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Endomembrane System
Includes nuclear membrane connected to ER connected
to cell membrane (transport)
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Ribosomes
• Made of PROTEINS and rRNA
• “Protein factories” for cell
• Join amino acids to make proteins
• Process called protein synthesis

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Ribosomes
Can be attached to
Rough ER
OR
Be free
(unattached)
in the
cytoplasm
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Golgi Bodies
• Stacks of flattened sacs
• Have a shipping side
(trans face) and
receiving side (cis face)
• Receive proteins made
by ER
• Transport vesicles with
modified proteins pinch
off the ends
CIS
TRANS
Transport
vesicle
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Golgi Bodies
Look like a stack of pancakes
Modify, sort, & package
molecules from ER
for storage OR
transport out of cell
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Golgi
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Golgi Animation
Materials are transported from Rough ER
to Golgi to the cell
membrane
by
VESICLES
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Lysosomes
• Contain digestive
enzymes
• Break down food,
bacteria, and worn out
cell parts for cells
• Programmed for cell
death (AUTOLYSIS)
• Lyse (break open) &
release enzymes to
break down & recycle
cell parts)
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Lysosome Digestion
• Cells take in
food by
phagocytosis
• Lysosomes
digest the food
& get rid of
wastes
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Cilia & Flagella
• Made of protein tubes
called microtubules
• Microtubules arranged
(9 + 2 arrangement)
• Function in moving
cells, in moving fluids,
or in small particles
across the cell surface
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80
Cilia & Flagella
• Cilia are
shorter and
more numerous
on cells
• Flagella are
longer and
fewer (usually
1-3) on cells
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Cell Movement with Cilia &
Flagella
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Cilia Moving Away Dust Particles from
the Lungs
Respiratory System
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Vacuoles
• Fluid filled
sacks for
storage
• Small or absent
in animal cells
• Plant cells have
a large Central
Vacuole
• No vacuoles in
bacterial cells
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84
Vacuoles
• In plants, they store
Cell Sap
• Includes storage of
sugars, proteins,
minerals, lipids,
wastes, salts, water,
and enzymes
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85
Contractile Vacuole
• Found in unicellular
protists like
paramecia
• Regulate water intake
by pumping out excess
(homeostasis)
• Keeps the cell from
lysing (bursting)
Contractile vacuole animation
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86
Chloroplasts
• Found only in producers
(organisms containing
chlorophyll)
• Use energy from
sunlight to make own
food (glucose)
• Energy from sun
stored in the Chemical
Bonds of Sugars
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87
Chloroplasts
• Surrounded by DOUBLE
membrane
• Outer membrane smooth
• Inner membrane modified
into sacs called
Thylakoids
• Thylakoids in stacks
called Grana &
interconnected
• Stroma – gel like material
surrounding thylakoids
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Chloroplasts
• Contains its own
DNA
• Contains enzymes
& pigments for
Photosynthesis
• Never in animal
or bacterial cells
• Photosynthesis –
food making
process
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89
Cell Size
Question:
Are the cells in an elephant
bigger, smaller, or about the
same size as those in a
mouse?
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90
Factors Affecting Cell Size
• Surface area (plasma membrane
surface) is determined by multiplying
length times width (L x W)
• Volume of a cell is determined by
multiplying length times width times
height (L x W x H)
• Therefore, Volume increases FASTER
than the surface area
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91
Cell Size
• When the surface area is no
longer great enough to get rid of
all the wastes and to get in
enough food and water, then the
cell must divide
• Therefore, the cells of an
organism are close in size
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92
Cell Size
Question:
Are the cells in an elephant
bigger, smaller, or about the
same size as those in a mouse?
About the same size, but …
The elephant has MANY MORE cells
than a mouse!
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